Unitised doses of dishwashing detergents are found to be more attractive and convenient to some consumers because they avoid the need of the consumer to measure the product thereby giving rise to a more precise dosing and avoiding wasteful overdosing or underdosing. For this reason automatic dishwashing detergent products in tablet form have become very popular. Detergent products in pouch form are also known in the art.
It is well known to use bleach in dishwashing detergent formulations in order to remove stains, especially tea, coffee, fruit juice and carotenoid stains. Chlorine and peroxygen bleaches are effective for stain removal. While chlorine bleach is a very effective cleaning agent, it is not compatible with a variety of detergent ingredients and may require additional processing in order to be incorporated into a final product. Peroxide bleaches on the other hand are more compatible with conventional detergent ingredients. However, one of the problems found when formulating peroxygen containing dishwashing detergent compositions is the fact that the bleach is liable to decompose in contact with moisture, thereby reducing the amount of active bleach available for the dishwashing process. Once the decomposition process is initiated, moreover, decomposition is auto catalysed by the presence of free radicals generated by the decomposition process. The products of bleach decomposition can also oxidise detergency enzymes, thereby reducing the amount of enzyme available for the dishwashing process.
In the case of flexible unitised doses such as pouches, capsules or sachets which are moisture permeable, bleach decomposition gives rise to an additional problem due to the generation of gaseous oxygen. Usually the pouch material is not permeable to oxygen and this can lead to bloating or even destruction of the pouch and to a detrimental effect on appearance and on dispenser fit.
Some detergent ingredients used in dishwashing detergent compositions are liquids. These liquid ingredients can be difficult or costly to include in a solid detergent composition. Also, certain ingredients are preferably transported and supplied to detergent manufacturers in a liquid form and require additional, and sometimes costly, process steps to enable them to be included in a solid detergent composition. An example of these detergent ingredients are surfactants, especially nonionic surfactants which are typically liquid at room temperature or are typically transported and supplied to detergent manufacturers in liquid form. Another example are organic solvents.
Current methods of incorporating liquid ingredients into solid detergent compositions include absorbing the liquid ingredient onto a solid carrier, for example by mixing, agglomeration or spray-on techniques. Typically, solid detergent compositions comprise only low amounts of these liquid detergent ingredients due to the difficulty and expense of incorporating these liquid ingredients into a solid detergent. The problems are particularly acute in the case of solid compositions which are subject to a densification step and especially to the levels of densification applied in machine dishwashing tablet manufacture. Furthermore, the incorporation of liquid ingredients into solid detergent compositions can impact on the dissolution characteristics of the composition (for example as the result of forming surfactant gel phases) and can also lead to problems of flowability. It would be advantageous to have a detergent composition which allows the different ingredients to be in their natural state i.e., liquid or solid. This would facilitate the manufacturing process and furthermore allow the delivery of liquid ingredients prior or post to the delivery of solid ingredients. For example differential dissolution of active ingredients would be beneficial in the case of enzyme/bleach compositions to avoid oxidation of enzymes by the bleach in the dishwashing liquor. It would also be advantageous to separate bleach from perfume.
An objective of the present invention is to provide dishwashing methods and products delivering improved cleaning performance and product stability. Another object is to provide dishwashing methods and products which have simplified processing, which allow for the problems of product incompatibility and which are capable of providing differential dissolution of active components.